Perform a deposit check, ensuring that the NPC has the given item and amount
in their inventory. If they do, the provided action is performed to
determine whether we should proceed. If the action chooses to proceed, then
we attempt to remove the items from the inventory. This may be fallible.
Finds the nearest chunk position that contains the appropriate kind of spot
for this courier quest variant. For example, if you have a Gnarling Carving
quest, this will search nearby for the nearest Gnarling Totem spot and
return the chunk position (not the world position, you’ll need to convert it
to wpos).